By N.Gopinath AP/CSE

 The data warehouse architecture is based on a relational database management system server that functions as the central repository for informational data.  Operational data and processing is completely separated from data warehouse processing.  This central information repository is surrounded by a number of key components designed to make the entire environment functional, manageable and accessible by both the operational systems that source data into the warehouse and by end-user query and analysis tools.

 The following are the seven components of a Data Warehouse:  Data Warehouse Database  Sourcing, Acquisition, Cleanup and Transformation Tools  Meta Data  Access (Query) Tools  Data Marts  DataWarehouseAdministration and Management  Information Delivery System

 The central data warehouse database is the cornerstone of the data warehousing environment.  Different technological approaches to the data warehouse database include: Parallel relational database designs for scalability that include shared- memory, shared disk, or shared-nothing models implemented on various multiprocessor configurations (symmetric multiprocessors or SMP, massively parallel processors or MPP, and/or clusters of uni- or multiprocessors). An innovative approach to speed up a traditional RDBMS by using new index structures to bypass relational table scans. Multidimensional databases (MDDBs) that are based on proprietary database technology. MDDBs enable on-line analytical processing (OLAP) tools that architecturally belong to a group of data warehousing components jointly categorized as the data query, reporting, analysis and mining tools.

 The data sourcing, cleanup, transformation and migration tools perform all of the conversions, summarizations, key changes, structural changes and condensations needed to transform disparate data into information that can be used by the decision support tool.  These tools also maintain the meta data. The functionality includes: Removing unwanted data from operational databases Converting to common data names and definitions Establishing defaults for missing data Accommodating source data definition changes

 Meta data is data about data that describes the data warehouse. It is used for building, maintaining, managing and using the data warehouse. Meta data can be classified into: Technical meta data, which contains information about warehouse data for use by warehouse designers and administrators when carrying out warehouse development and management tasks. Business meta data, which contains information that gives users an easy-to-understand perspective of the information stored in the data warehouse.

Query and Reporting tools can be divided into two groups: Reporting Tools and Managed Query Tools Reporting tools can be further divided into production reporting tools and report writers.  Production reporting tools let companies generate regular operational reports or support high-volume batch jobs such as calculating and printing paychecks.  Report writers, on the other hand, are inexpensive desktop tools designed for end-users. Managed query tools shield end users from the complexities of SQL and database structures by inserting a meta-layer between users and the database. These tools are designed for easy-to-use, point-and-click operations that either accept SQL or generate SQL database queries.

 The term data mart means different things to different people.  A rigorous definition of this term is a data store that is subsidiary to a data warehouse of integrated data.  The data mart is directed at a partition of data (often called a subject area) that is created for the use of a dedicated group of users.  These could be classified in two categories: Dependent Data Marts Independent Data Marts

 Dependent data mart A subset that is created directly from a data warehouse  Independent data mart A small data warehouse designed for a strategic business unit or a department

 Managing data warehouses includes: 1. Security and priority management 2. Monitoring updates from the multiple sources 3. Data quality checks 4. Managing and updating meta data 5. Auditing and reporting data warehouse usage and status 6. Purging data 7. Replicating, sub-setting and distributing data 8. Backup and Recovery and 9. Data warehouse storage management.

The information delivery component is used to enable the process of subscribing for data warehouse information and having it delivered to one or more destinations according to some user- specified scheduling algorithm. Delivery of information may be based on time of day or on the completion of an external event. The rationale for the delivery systems component is based on the fact that once the data warehouse is installed and operational, its users don't have to be aware of its location and maintenance.

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